Dissolved oxygen (DO) is generally regarded as a proxy for the overall health of a river from the perspective of organic and nutrient loading. When organic loading is high and DO concentrations become a concern, mitigation options may be required such as artificial aeration through oxygen injection into waste streams. We evaluate the effectiveness of a pilot oxygen injection program and surface aeration at the open-water lead downstream of the Al-Pac's effluent diffuser. With the parameters obtained from the literature, a modified Streeter-Phelps model described the spatial variation of DO downstream of the diffuser. Reaeration from the open-water lead, formed as a result of effluent temperature, was significant and the importance of accurate prediction of its size is therefore important to managing effluent effects. The amount of DO added to the river due to artificial aeration at rates of 3500 and 5000 lb per day was about 55 and 27% of that due to surface reaeration of a 4 and 5-km long open water lead, respectively. The artificial aeration technique evaluated here appears to have higher absorption efficiencies than those for conventional air injection systems. The results of this study are important for future work to develop accurate DO models for ice-covered rivers, and in developing and evaluating oxygen injection systems.